Depletion of SK-1 promotes EC maturation. (A) BM was harvested from WT and SK-1-KO mice, the Lin⁻/c-kit⁺ cells isolated by magnetic sorting. Results show the mean plus or minus SEM isolated from 6.5 × 10⁷ cells per group from 3 separate experiments. (B) BM cells from WT and SK-1-KO mice (solid and broken lines, respectively) were examined for their ability to take up Ac-LDL at days 3 and 9 after seeding. Results show the mean plus or minus SEM of the percentage uptake. *P < .05, compared with WT day 3. #P < .05, compared with WT day 10, 1-way analysis of variance. (C) Flow cytometric analysis of Ac-LDL uptake by WT (thin line) and SK-1-KO (thick line) BM cells after 3 days of culture from a representative of 3 experiments performed. (D) WT and SK-1-KO mBM cells (□ and ■, respectively) were harvested for Sca-1 surface expression and VE-cadherin mRNA expression analysis by flow cytometry and quantitative RT-PCR, respectively. Messenger RNA results are normalized to their PPIA gene. Data are expressed as mean plus or minus SEM from 3 separate experiments for Sca-1 surface expression (at day 7 after seeding) and VE-cadherin mRNA levels (at day 10 after seeding). *P < .05, compared with WT levels on day of harvest. (E) Six-day cultured BM cells were seeded into Matrigel. Images depict tube formation after 5 and 30 hours and are representative of 5 separate experiments. Inset numbers reflect mean plus or minus SEM of total tubes formed at 30 hours from 5 experiments.